Method of and apparatus for producing wood chips

ABSTRACT

Pieces of wood are fed to the orbit of a cutter blade by a feed shaft having one side forming a relatively flat angle (obtuse angle) with the orbit (and inclined counter to the direction of rotation) and another side opening substantially radially (i.e., at a right angle) into the orbit. Drive chains are provided on these sides to advance the pieces of wood on the one side at a higher rate than the pieces on the other side so as to produce chips of like thickness. The column is curved back over the cutter and the chains are driven from a common center which is also the center of curvature for both sides.

United States Patent [1 1 [111 3,866,645

Sybertz 1 Feb. 18, 1975 [54] METHOD OF AND APPARATUS FOR 2,849,038 8/1958 Clark 144 172 PRODUCING WOOD CHIPS 2,969,095 1/1961 Brookhyser et aL. 144/172 X 3,2l9,076 ll/l965 Logan etal 144/42 [75] Inventor: ans Sy Hargeshelm, 3,237,663 3/1966 Kirsten 144/172 Germany [73] Assignee: Hombak Maschinenfabrik KG, Bad Primary Efami'gler' Andrew Juhasz Kreuznach, Sandweg, Germany Assistant bxamzner-W. D. Bray Attorney, Agent, or FirmKarl F. Ross; Herbert [22] Filed: Feb. 13, 1973 Dubno [21] Appl. No.: 332,108

[57] ABSTRACT 30] Foreign Application p i i Data Pieces of wood are fed to the orbit of a cutter blade by F 9 n 0 a feed shaft having one side forming a relatively flat eb 19 l 72 Germany 22 7901 angle (obtuse angle) with the orbit (and inclined [52] U CL 144/326 C 144/162 R 144/172 counter to the direction of rotation) and another side l44/242R 241/28 541/292 opening substantially radially (i.e., at a right angle) [51 Int. Cl. .1 B27C 9/60 the OFhh- Drive Chains Provided these Sides [58] Field of Search 241/28, 292.1; 144/162 R, 9 advahh-e the Piece? of Wood on the "1 Side at 8 144/162 A, 162 B, 167, 43 42, 242 R, 242 hlgher ratethan the PIICS on the: other side so as to B 172 326 R 326 B 326 A 326 C 323 produce chlps of hke thickness. The column is curved back over the cutter and the chains are driven from a [56] References Cited commoncenter which is also the center of curvature for both sides. UNITED STATES PATENTS 2,784,753 3/1957 Kliem et al. 144/42 10 Clalms, 3 Drawing Flgures 20.0 x I a METHOD OF AND APPARATUS FOR PRODUCING WOOD CHIPS FIELD OF THE INVENTION The present invention relates to a method of and an apparatus for comminuting wood. More particularly, this invention relates to a system for reducing pieces of wood to chips.

BACKGROUND OF THE INVENTION In the production of chipboard (pressed board formed from wood chips and a binder) one of the primary concerns is that the chips should be of like (uniform) thickness. Chips that are too thin make the finished board too expensive since increased quantities of binder are required, and chips that are too thick make it difficult to produce a board which is completely planar on both faces or to further subdivide the chips into fibers of uniform character. In general, for this and other purposes, it is desirable to produce large quantities of wood chips of the greatest possible uniformity with respect to chip thickness.

The most effective method of reducing pieces of wood, usually logs previously cut into lengths of convenient size, to chips is by means of comminuting machines of either of two general types, both arranged so that the wood fibers run longitudinally of the chips. The machine that produces the most uniform chips comprises a disk-type blade such that the rates of feed of the pieces of wood at all parts of the blade are equal and the blades each have a constant depth or projection height at all parts of their travel. However, even with a disk some 3 meters in diameter, the wood pieces or logs must be cut to limited lengths for such machines, substantially increasing production costs.

In another arrangement, which is frequently preferred to the above because it can chip much longer pieces of wood, a horizontal shaft or drum is provided on its periphery with one or more outwardly projecting blades whose cutting edges define a cylindrical orbit spaced radially from and coaxially with the drum. The logs are fed down onto this generally cylindrical cutter shaft or drum with their axes parallel to the axis of rotation of the blade carrier. Although this arrangement can be used with logs as long as, say, 2 meters, with a 3-meter long drum, chips so produced are of different or varying thicknesses. Customarily, this disadvantage has been accepted in view of the advantage of increased output.

OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide an improved method of and an improved apparatus for for reducing pieces of wood to chips.

Another object of the invention is the provision of a system for producing chips of substantially uniform thickness from pieces of wood or timber of relatively large length at a high rate.

Yet another object of the invention is to provide an improved chipper of the drum type so that it produces chips of like thickness.

SUMMARY OF THE INVENTION These objects are attained by the present invention which is based on the discovery that the reason drumtype wood chippers do not produce chips of like thickness is because the pieces of wood fed to the cutter in LII A the changing velocity component of the blade in the radial direction as the blade sweeps through the aforementioned segment of the orbit arc subtended by the feed chute.

The present invention overcomes this characteristic by providing means in the feed chute which advances those work-pieces arriving more tangentially than radially at a faster rate than the other workpieces. The result is a surprising uniformity in thickness in the chips. The invention thus provides for advancing the column of wood toward the orbit of the blades at rates proportional to the radial velocity component thereof across the aforementioned segment of the orbit arc.

According to this invention, the apparatus has a feed shaft having one side which forms a flatter angle with the orbit of the cutter than the other side, and means (e.g., an endless conveyor) on this side serves to advance the pieces of wood engaging it faster than those engaging the opposite side of the shaft. This other side of the shaft is generally radial to the cutter orbit.

In accordance with yet another feature of my inven' tion, the shaft is substantially rectangular in section and curved with one end opening downwardly into the orbit of the cutter and the other end extending substantially horizontally off to the side. Such an arrangement substantially reduces the height of the chipping apparatus. Furthermore, both sides have the same center of curva ture so that toothed chains acting as the feed means on these sides can be carried on respective sprockets on a common shaft, and the chains will move at different speeds for even chip production. The logs are generally parallel to the cutter axis as they are delivered to the cutter so that the chips have their fibers parallel to the line of cut.

DESCRIPTION OF THE DRAWING The above and other objects, features and advantages will become apparent from the following description, reference being made to the accompanying draw ing in which:

FIG. 1 is an end view of an embodiment of the present invention;

FIG. 2 is an end view of another embodiment of the present invention; and

FIG. 3 is a view of the embodiment of FIG. 2 in reduced scale.

As shown in FIG. 1. a cutter comprises a drum 1 carrying a blade 2. See copending Patent Application Ser. No. 333,691 filed Feb. 20, 1971 for a more detailed description of the attachment of the blade 2 in the drum 1, and US. Pat. No. 3,199,799 issued Aug. 10, 1965. The cutting edge 2a defines with the cylindrical drum 1 an orbit O spaced from the drum 1 by a distance a. A motor 9 rotates the drum 1 counterclockwise as shown in FIG. 1 about a horizontal axis A.

In normal installations a column of logs 3 is fed down onto the cutter 1, 2 in an upright. shaft 4 at a constant speed S such that for each revolution of the blade 2 the logs 3 are displaced through a distance a, here equal to a. The logs 3 therefore come into the cutter orbit O over an arc 8 ending at one end in a vertical plane P passing through the axis A and here coinciding with the side 4a of the shaft 4.

Chips C will be cut from the logs 3 and expelled tangentially horizontally to the left, as seen in FIG. 1. In prior-art arrangements these chips would be of different thicknesses because those chips cut from the logs adjacent the wall 4a would have a thickness equal to a whereas those chips cut from the region x adjacent the other side 4b will be of lesser thickness because the blade 2 will cut these latter chips at a flatter angle and they will only have advanced part of the way into the drum 1. More specifically, the displacement VI in the prior-art is not enough to accommodate the distance a at the flat angle a with which the side 4b meets the orbit 0.

According to the present invention, the logs 3 against the side 4b of the shaft 4 are advanced with a velocity component imparting to them a displacement V2 in a unit of time which is greater than the displacement per unit time VI of the logs on the opposite side 4a of the shaft by the displacement per unit time AV. This greater displacement V2 enables the logs to pass from the orbit O to the drum 1 even at the flat angle a, at a speed corresponding to the velocity component of the blade in this region.

Displacement of the logs directly engaging the side 4b at this faster rate will impart to the logs 3 in the shaft 4 velocity such that their displacement per unit time will vary between V1 and V2. The result is a surprisingly uniformed chip thickness.

FIG. 2 shows an embodiment of the present invention having substantially similar structure to that of FIG. 1, with like reference numerals being used for like structure. In this embodiment, however, a curved input shaft 5 has an inner wall 5a and an outer wall 5b provided with respective toothed feed chains 6a and 6b which are carried on respective sprocket wheels a, 10b (FIG. 3) carried on a common shaft 7 driven by a motor 11 at the same angular velocity. This shaft 7 defines the center of curvature of the arcuate walls 50 and 5b of the shaft 5 which has an inlet 5c opening horizontally and receiving logs 3 from a conveyor 12. The wheel 10a has a radius R1 and the wheel 10b a radius R2. The proportion R11R2 VI:V2 so that regardless of the angular velocity of shaft 7 the correct ratio is maintained between the two feed speeds. Two wheels 10a and two wheels 10b flank the drum 1, only one of each wheel being shown in FIG. 3.

Since the grip the chains 6a and 6b can get on the logs 3 is largely dependent on how full the shaft 5 is, it is common practice to provide as long a shaft 5 as possible. The cross-sectional area of the shaft is, however, also dependent on the size of the cutter l, 2; the larger the cutter the larger the shaft must be in order to supply logs to it rapidly enough. The curved shaft 5 of the present invention allows a relatively long shaft to be employed which does not, however, take up a great deal of space above the apparatus so that a conventional delivery apparatus may be employed. Usually these input devices are built for relatively low arrangements so that when a new, larger capacity cutting machine is installed the whole system must be rebuilt.

l claim:

1. A method of reducing pieces of wood to chips comprising the steps of:

rotating an elongated cutter blade about an axis whereby the cutting edge of said blade defines an orbit;

feeding pieces of wood to said cutter in a column having a pair of sides, one of said sides forming a flatter angle with said orbit than the other of said sides; and

advancing said pieces of wood toward said cutter more rapidly at said one side than at said other side.

2. The method defined in claim 1 wherein the pieces of wood on said other side enter said orbit generally radially.

3. The method defined in claim 2 wherein said sides are displaced toward said blades at different rates to advance said pieces at said one side more rapidly.

4. An apparatus for reducing pieces of wood to chips comprising:

a rotatable cutter blade having a cutting edge;

means for rotating said blade about an axis to define an orbit with said edge;

a feed shaft opening at said orbit and having one side forming a flatter angle with said orbit than the other side; and

means on said feed shaft for advancing pieces of wood along said one side toward said orbit with a first predetermined velocity and for advancing pieces of wood along said other side with a second predetermined velocity slower than said first velocity.

5. The apparatus defined in claim 4 wherein said shaft and said sides are arcuate.

6. The apparatus defined in claim 5 wherein said means on said shaft include chains running along said sides.

7. The apparatus defined in claim 6 wherein said sides have a common center of curvature, said means on said shaft including drive means at said center for operating both of said chains.

8. The apparatus defined in claim 5 wherein said shaft has a downwardly Opening outlet end at said orbit and a generally horizontal opening inlet end.

9. The apparatus defined in claim 4 wherein the pieces of wood against said other side enter said orbit in a substantially radial direction, said one side being spaced further from a plane passing through said axis and parallel to said direction further than said other side.

10. In a method of comminuting wood wherein a column thereof is fed toward a generally cylindrical cutter-blade orbit over an arc segment thereof in a feed direction, said column spanning an arc segment of said orbit and the velocity component of said blade counter to said direction being greater at one side of said column than the other side in the sense of blade rotation, the improvement which comprises the step of advancing the column of wood at said one side into said orbit at a greater speed than that of said other side and dimensioned to counteract the greater velocity component of the blade so that wood chips of uniform thickness are produced. 

1. A method of reducing pieces of wood to chips comprising the steps of: rotating an elongated cutter blade about an axis whereby the cutting edge of said blade defines an orbit; feeding pieces of wood to said cutter in a column having a pair of sides, one of said sides forming a flatter angle with said orbit than the other of said sides; and advancing said pieces of wood toward said cutter more rapidly at said one side than at said other side.
 2. The method defined in claim 1 wherein the pieces of wood on said other side enter said orbit generally radially.
 3. The method defined in claim 2 wherein said sides are displaced toward said blades at different rates to advance said pieces at said one side more rApidly.
 4. An apparatus for reducing pieces of wood to chips comprising: a rotatable cutter blade having a cutting edge; means for rotating said blade about an axis to define an orbit with said edge; a feed shaft opening at said orbit and having one side forming a flatter angle with said orbit than the other side; and means on said feed shaft for advancing pieces of wood along said one side toward said orbit with a first predetermined velocity and for advancing pieces of wood along said other side with a second predetermined velocity slower than said first velocity.
 5. The apparatus defined in claim 4 wherein said shaft and said sides are arcuate.
 6. The apparatus defined in claim 5 wherein said means on said shaft include chains running along said sides.
 7. The apparatus defined in claim 6 wherein said sides have a common center of curvature, said means on said shaft including drive means at said center for operating both of said chains.
 8. The apparatus defined in claim 5 wherein said shaft has a downwardly opening outlet end at said orbit and a generally horizontal opening inlet end.
 9. The apparatus defined in claim 4 wherein the pieces of wood against said other side enter said orbit in a substantially radial direction, said one side being spaced further from a plane passing through said axis and parallel to said direction further than said other side.
 10. In a method of comminuting wood wherein a column thereof is fed toward a generally cylindrical cutter-blade orbit over an arc segment thereof in a feed direction, said column spanning an arc segment of said orbit and the velocity component of said blade counter to said direction being greater at one side of said column than the other side in the sense of blade rotation, the improvement which comprises the step of advancing the column of wood at said one side into said orbit at a greater speed than that of said other side and dimensioned to counteract the greater velocity component of the blade so that wood chips of uniform thickness are produced. 